1. Field of the Invention
The present invention relates to synthetic filaments having a distinctive bilobal cross-sectional shape. The filaments are especially suitable for making carpets which exhibit a silk-like luster and have a soft hand.
2. Description of Related Art
The majority of carpets used in residences are referred to as cut-pile carpets. In such carpets, heat-set, ply-twisted, pile yarn is inserted into a backing material as loops which are then cut to form vertical tufts. The tufts are then evenly sheared to a desired height which is typically about 0.4 to 0.7 inches.
Today, there are numerous cut-pile carpet styles available, depending upon where the carpet is to be installed. For instance, in areas where there is a high level of traffic, such as hallways and stairs, frieze-type carpets are often used. These carpets are made from ply-twisted pile yarns having a high degree of twist. Generally, such carpets have a firm, dense "hand" and show good durability. By the term, "hand", it is meant the tactile qualities of the carpet such as softness, firmness, elasticity and other qualities perceived by touch. In living rooms, textured saxony-type carpets having good durability, as well as a plusher, more luxurious hand are often used.
For bathrooms, there is a particular need for carpets which have a soft and comfortable texture. As used herein, the term "carpet" includes floor coverings having pile yarns and a backing system as well as rugs which may or may not have a secondary backing. It is also important that such carpets have good "washfastness" since they are subjected to frequent washing and drying. By the term "washfastness" as used herein, it is meant the resistance of the dyed carpet to loss of color during laundering.
Those skilled in the art have considered different ways for preparing carpets having a softer, more comfortable hand. For instance, it is known to use multifilament yarns having a denier per filament (dpf) of about 4.5 dpf in order to obtain such an effect. However, these finer dpf yarns are more difficult to manufacture than coarse dpf yarns, especially in bulked continuous filament (BCF) yarn-making operations. This translates into higher total production costs for the finished carpet. Moreover, finer dpf yarns tend to have poor washfastness and newness retention due to the increased surface area of the filaments.
In addition, Jamieson, U.S. Pat. No. 3,249,669, describes making fabrics from polyester multifilament yarn bundles, wherein the filaments have different cross-section shapes. Thus, filaments having round cross-sections are combined with filaments having Y-shaped cross-sections. The fabrics are described as having more bulk and a "pleasing hand" versus yarns of homogeneous filament cross-sections.
Kimura et al., U.S. Pat. No. 4,416,934 describes a woven or knitted polyester multifilament fabric having a silk-like appearance and touch. The fabric is composed of polyester multifilament yarns each containing filaments of an irregular cross-sectional profile, e.g., trilobal, star-shaped, C-shaped, L-shaped, or V-shaped cross-sections.
In Bagnall, U.S. Pat. No. 3,508,390, filaments having a Y-shaped cross-section are described. The filaments may be prepared from synthetic polymers, such as polyamides and polyesters, and may be used in floor covering materials. Fabrics prepared from such filaments are described as having excellent dyeability and may have a silk appearance and dry, soft hand depending upon its intended use.
Now, in accordance with the present invention, there are provided filaments having distinctive bilobal cross-sections. Yarn bundles containing said filaments may be used to prepare carpets having good bulk and a soft hand. The carpets also exhibit a silk-like luster with low glitter and good color depth By the term "luster" it is meant the overall glow of the carpet from reflected light By the term "glitter" it is meant the specks of light perceived on the carpet when intense light is directed at the carpet. This is due to minute fiber sections acting as mirrors or reflecting prisms. Carpets are often referred to as having a bright or dull luster, but both types of carpets may have a high degree of glitter. "Color depth" refers to the color's degree of intensity. It has further been found that the carpets of this invention also demonstrate good washfastness.